1. Field of the Invention
The present invention relates to a circular fluorescent lamp unit and a lighting apparatus using this circular fluorescent lamp unit.
2. Description of the Prior Art
So far, the circular outer diameters of the glass bulbs of circular fluorescent lamp units commonly put to use has been, for example, 225 mm for 30 W, 299 mm for 32 W and 373 mm for 40 W, with the tube outer diameters of the respective glass bulbs being 29 mm.
Lighting apparatus using this circular fluorescent lamp unit is disclosed in Japanese Unexamined Patent Publication No. 4-212276. In the lighting apparatus, an apparatus body with a truncated cone configuration is provided on a lower surface of a top board. A socket and lamp holder are symmetrically provided so as to project downwardly from this apparatus body. A base of a circular fluorescent lamp unit is connected to this socket and a glass bulb portion opposed to the base of the circular fluorescent lamp unit is fitted in the lamp holder. The circular fluorescent lamp unit is arranged below the apparatus body. In this state, a high-frequency power is fed from a high-frequency lighting circuit such as an inverter lighting circuit built in the apparatus body to the circular fluorescent lamp unit so that the circular fluorescent lamp unit turns on a light.
Meanwhile, recently, in order to make the visual environments in a dwelling space comfortable, the tendency has been toward the size reduction and thickness reduction of goods for the interiors. The lighting apparatus is also a portion of the interior goods, and is increasingly required to reduce its thickness so that it is as if the ceiling surface seems to be high.
However, in the prior lighting apparatus which is of the type in that a circular fluorescent lamp unit is located within an apparatus body, it is difficult to reduce the thickness of the whole apparatus including the circular fluorescent lamp unit.
More specifically, since the circular fluorescent lamp unit needs a lamp holder and a lamp socket for its connection and holding, a large space in the vertical directions is necessary. As a result of that, the thickness of the apparatus body is relatively enlarged. In addition, since the common circular fluorescent lamp unit has a tube outer diameter of 29 mm, limitation is imposed on fabricating a lighting apparatus with a desirable thickness.